Compounds having absorption with a high intensity against specific light are used as optical elements in recording layers of optical recording media such as CD-Rs, DVD-Rs, DVD+Rs and BD-Rs, and in image display devices such as liquid crystal display devices (LCDs), plasma display panels (PDPs), electroluminescence displays (ELDs), cathode ray tube display devices (CRTs), fluorescent display tubes and field emission-type displays.
In optical filters for image display devices such as liquid crystal display devices (LCDs), plasma display panels (PDPs), electroluminescence displays (ELDs), cathode ray tube display devices (CRTs), fluorescent display tubes and field emission-type displays, various compounds that absorb light at a wavelength of 300 to 1,100 nm are used as light absorbing materials.
Furthermore, in recent years, light absorbers that selectively absorb a wavelength at specifically 380 to 500 nm are required so as to impart sufficient color purity and color separation to display devices and to improve image quality of images. For these light absorbers, specially precipitous light absorption, i.e., a small half width of λmax, and avoidance of loss of functions due to light, heat and the like are required.
Optical filters that are mainly used in liquid crystal display devices (LCDs) include color filters. Although three primary colors of RGB have been generally used in color filters, it is difficult to impart hues of pure RGB by a single color material, and efforts to obtain hues that are close to those of pure RGB have been made by using plural color materials. Therefore, color materials of yellow, orange, purple and the like are also required besides RGB.
As light absorbers used in color filters, organic and/or inorganic pigments have been used due to their high heat resistance; however, they have a problem that they decrease the luminance of display devices since they are pigments, and this problem has been solved by increasing the luminance of a light source. However, in accordance with the trend of reduction of power consumption, dyes having excellent solubility in solvents and resin compositions and having high heat resistance, and color filters using the dyes have been developed actively. Patent Literatures 1 to 3 disclose dyes each using a compound having a specific structure. Patent Literature 4 discloses an optical filter using a compound having a specific structure.
However, the dyes (compounds) described in these literatures were not satisfiable from the viewpoints of solubility and heat resistance.